Freud's dream theory:
1. Dreams are the gateway to the subconscious
Dreams are the realization of people's subconscious wishes.
2. There are some rules for the expression of subconscious mind in dreams.
In the subconscious, many people have repressed instincts, including sex, violence, etc. These instincts are not tolerated by social moral concepts. But these suppressed contents also need ways of expression. Therefore, only when people's control over their thoughts weakens during sleep, will these repressed contents appear in the form of dreams.
Concept: Death is not the end, but death is a nightmare